1. Field of the Invention
Aspects of the present invention relate to an electron emission device, an electron emission display device including the electron emission device and a method of driving the electron emission device, and more particularly, to an electron emission device that is driven at a low voltage, has low power consumption, and can be mass-produced, an electron emission display device including the electron emission device, and a method of driving the electron emission device.
2. Description of the Related Art
Generally, electron emission devices use a thermal cathode or a cold cathode as an electron emission source. Electron emission devices that use a cold cathode as an electron emission source include field emission device (FED) type devices, surface conduction emitter (SCE) type devices, metal insulator metal (MIM) type devices, metal insulator semiconductor (MIS) type devices, ballistic electron surface emitting (BSE) type devices, etc.
An FED type electron emission device uses the principle that, when a material having a low work function or a high β function is used as an electron emission source, the material readily emits electrons in a vacuum due to an electric potential. Devices that employ a tapered tip structure formed of, for example, Mo, Si as a main component, a carbon group material such as graphite, diamond like carbon (DLC), etc., or a nano structure such as nanotubes, nano wires, etc., have been developed.
In an SCE type electron emission device, an electron emission source includes a conductive thin film having a nano-size gap between first and second electrodes disposed parallel to each other on a substrate. The electron emission device makes use of the principle that electrons are emitted from the micro cracks, which are electron emission sources, when a current flows on the surface of the conductive thin film due to a voltage being applied between the electrodes.
MIM type electron emission devices, which have a metal-dielectric layer-metal (MIM type) structure and MIS type electron emission devices, which have a metal-dielectric layer-semiconductor (MIS type) structure, make use of the principle that when voltages are applied to two metals having a dielectric layer therebetween or to a metal and a semiconductor having a dielectric layer therebetween, electrons migrate from the metal or the semiconductor having a high electron potential to the metal having a low electron potential.
A BSE type electron emission device includes an electron emission source that makes use of the principle that electrons travel without scattering when the size of a semiconductor is smaller than the mean-free-path of electrons in the semiconductor. To form the electron emission source, an electron supply layer formed of a metal or a semiconductor is formed on an ohmic electrode, and an insulating layer and a metal thin film are formed on the electron supply layer. When a voltage is applied between the ohmic electrode and the metal thin film, the electron emission source emits electrons.
FIG. 1 is a partial perspective view of a conventional electron emission display device 100 that uses an FED type electron emission device 101. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIG. 3 is an enlarged view of a portion III of FIG. 2.
Referring to FIGS. 1 and 2, the electron emission device 101 includes a first substrate 110, a plurality of cathode electrodes 120, a plurality of gate electrodes 140, a first insulating layer 130, and a plurality of electron emission sources 150.
The first substrate 110 is a board having a predetermined thickness. The cathode electrodes 120 extend parallel to each other on the first substrate 110 and may be formed of common electrically conductive materials. The gate electrodes 140 are disposed above the cathode electrodes 120 with the first insulating layer 130 therebetween, and, like the cathode electrodes 120, may be formed of common electrically conductive materials.
The first insulating layer 130 is interposed between the gate electrodes 140 and the cathode electrodes 120 to prevent a short circuit between the gate electrodes 140 and the cathode electrodes 120.
The electron emission sources 150 are electrically connected to the cathode electrodes 120, and disposed below the gate electrodes 140. The electron emission sources 150 may be formed of a carbon material or a nanomaterial.
The electron emission device 101 can be used in the electron emission display device 100, which creates an image by generating visible light. The electron emission display device 100 further includes a front panel 102 parallel to the first substrate 110 of the electron emission device 101. The front panel 102 includes a second substrate 90, an anode electrode 80 disposed on the second substrate 90, and phosphor layers 70 disposed on the anode electrode 80.
In the electron emission display device 100, a high voltage is applied to the gate electrodes 140 such that the electron emission sources 150 emit electrons. The high voltage applied to the gate electrodes 140 increases not only the power consumption but also the manufacturing costs since integrated devices suitable for high-voltage driving are required for a driving circuit, and such devices are expensive.